This invention relates to a method for the treatment of an aqueous liquid, whereby the liquid is subjected, during circulation between two opposing electrodes separated from the liquid by means of insulation material, to the effect of an electrical field formed by connecting the electrodes to a dc-high-voltage potential, particularly for the removal of boiler scale and corrosion, or for the prevention of the formation of boiler scale and corrosion in the containers or pipe systems through which the treated liquid flows. In addition, the invention relates to a device for the execution of the method with a treatment chamber having an inlet and outlet and with two electrodes, arranged opposite each other on either side of the treatment chamber and electrically insulated from the treatment chamber, as well as with an electrical dc-high-voltage sourse connected to the electrodes.
Because of substances of various kinds that are contained in water, particularly lime dissolved in water, boiler scale and corrosion are caused in containers and pipes in which water is exposed to physical effects, such as intensive heating in hot-water boilers and steam kettles. It is known that countermeasures can be taken against the unwanted precipitation of substances contained in the water which result in boiler scale, and against the formation of corrosive properties of the water by subjecting the water, before it reaches the containers or pipes in which it is exposed to special conditions, to the effect of an electrical and/or magnetic field. By this means it is possible to reduce, to a greater or lesser extent, the tendency for the development of corrosive properties of the water, and it is also possible to reduce again the extent of boiler-scale formation and corrosion, produced in containers or pipes by supplying them with untreated water, by supplying the containers or pipes with water treated as described above. The extent of the effect of the treatment of water or aqueous liquids with magnetic and/or electrical fields depends also significantly on the intensity of the physical conditions acting on the water of or the aqueous liquid after such a preliminary treatment. Thus, for example, the effect that can be achieved with techniques that have become known up to now decreases in proportion to the thermal load to which the pretreated water is subjected. Various known devices have only a slight effect and very often these devices have a relatively costly construction and require constant and costly maintenance, and for this reason alone they are scarcely suitable for general use. Many of these devices require that a special prefilter be installed ahead of them, and this results in additional procurement and maintenance costs.
From GB-A 1 274 902 a device of the above described type is known, in which the two electrodes, separated from the liquid by insulating material, are connected to the two opposing polarity carrying clamps of a dc-voltage source. This reference also mentions the possibility of separating only one of the two electrodes of such a device from the liquid by means of insulating material. A preferred embodiment has several sequentially arranged treatment units, each with two electrodes, separated from the liquid by insulating material, whereby two dc-voltage fed treatment units are followed by one fed with ac-voltage.
From U.S. Pat. No. 4,073,712 a device for the electrostatic treatment of water is known, in which the liquid to be treated is led through an annular gap formed between two coaxially arranged cylindrical electrodes, whereby both electrodes are separated from the liquid by means of insulating material and connected to the two clamps with opposing polarity of a dc-voltage source.
In addition, a device is known from BE-A 465 481 in which a flowing liquid is exposed to the effect of an electrical alternating field. In this device the liquid flows through a glass tube, on the outside of which, thus separated from the liquid, an electrode is arranged which is connected, as is an electrode located coaxially inside the tube within the liquid, to an ac-voltage source.